Cause of 1770's 'sinkhole' identified

THE POTENTIAL sink hole discovered at Seventeen Seventy last month has been examined by Gladstone Regional Council - and investigators have come to some wonky conclusions.

Council officers have concluded the mysterious underwater apparition is likely to be a freshwater spring, otherwise known as a "wonky hole".

Wonky holes are formed when groundwater from land-bound aquifers is discharged into the sea.

That set of circumstances becomes increasingly likely after large amounts of rain, such as those experienced on the Discovery Coast over the least few weeks.

The hole at Seventeen Seventy is believed to be only a few metres across, with a lot of shell and rubble around the outside.

Senior conservation officer Rebecca Hendry said the location of freshwater springs was often associated with ancient river channels.

"At the end of the last ice age the sea level rose as the ice melted and the rivers that once flowed drowned under the ocean and were covered over by sediments," she told The Observer.

"The groundwater of today will still follow the ancient paths of the rivers and the ancient mouths of the rivers will occasionally pop up under the sea after rain events due to the increased flow and amount of groundwater."

There are more than 200 known wonky holes in the waters of northeast Australia, Ms Hendry said.

"There is a freshwater spring that pops up from time to time at Endeavour Park that is in line with the position of the undersea wonky hole," she said.